Acta Psychologica 53 ( 1983) 177- 182

North-Holland 177

PSYCHOLOGY AND PHYSICS: A REPLY TO OUR CRITICS*

Stephen WILCOX

Franklin & Marshall College, USA

David A. EDWARDS

University of Georgia, USA

Accepted February 1983

One of the central themes of our original article (Wilcox and Edwards 1982) was that different people see things differently. This point is illustrated by the three replies to the article. De Wit and de Swart (1983) fault us for proposing any form of realism; Hudson (1983) faults us for rejecting traditional scientific realism; Haber (1983) faults us for misunderstanding the whole scientific enterprise and goes on to claim that the truth of our brand of realism is so obvious that it is “held by most, if not all, psychologists and other scientists”. Before addressing each of these replies, specifically, let us try to clarify some of the issues surrounding realism.

The central claim of realism, as we use the term, is that the objects of experience are not inherently, private, are not causally dependent upon the experiencer (qua experiencer), and, thus, are potentially manipula- ble by a third party (e.g., a psychologist) [l]. This is what we meant by

* Mailing address: S. Wilcox, Dept. of Psychology, Franklin & Marshall College, Lancaster, PA 17604, USA.

[l] Of course, at any given time, we tend to distinguish between “objective” objects such as tables

and “subjective” objects such as idiosyncratic imaginings. However, our position is that this

distinction is itself dependent upon what we tend to agree about, use in certain ways rather than

others, etc. In other words, “ subjectivity” (or “objectivity” for that matter) is context-dependent

and cannot, therefore, function as a fundamental ontological category. As psychologists, we may

not be particularly interested in certain objects of experience, or we may not be willing to invest

the time required to see them as objective, but this does not mean that we are forced to treat some

experiences as “internally generated” and embark on a search for the “mental processes” which

make such generation possible.

000 l-69 1 S/83/$3.00 0 1983, Elsevier Science Publishers B.V. (North-Holland)

178 S. Wilcox, D.A. Edwards / Psychology and physics: a reply

“the objects of experience are properties of the world”. Realism has

two distinct advantages. First, it doesn’t force us to reject our intuition that, in an important sense, the world is just “there” to be discovered. Also, it gives the psychologist some hope that he or she will be able to do more than make up interesting stories about what is in people’s heads.

On the other hand, most forms of realism make some sort of primary-secondary distinction - some a priori claim about what is real and what isn’t, which inevitably leads into a whole morass of problems. Gibson’s idea (and John Dewey’s before his) was that one could be a realist, in the sense mentioned above, but still maintain that any primary-secondary distinction is only relevant to some particular con- text, that the designation of what is real and what isn’t is always dependent upon one’s purposes, one’s needs, one’s point of view. In Gibson’s view (and ours), the world goes on about its business, but we experience only that small portion of its structure which is relevant to us, and only some of that at any given time.

Therefore, one can never say in the abstract what the world is made of. The answer must always be that it depends upon the organism/per- son with reference to whom the world is described. And, in the case of the psychologist, there are really two points of view to be taken into consideration - the point of view of the organism under study which is seen from the point of view of the psycholoigst himself: An adequate environmental description must have predictive consequences vis a vis the organism in question for the psychologist. Our original point was that traditional physics won’t do for this environmental description.

De Wit and de Swart characterize our position as something rather different. They begin by accusing us of saying that psychology should rely upon some form of physics, a claim that they find both false and a misleading use of the “idea of reliance”. But since the only claim we made was that a theory of environment must be a part of psychology (a claim they endorse), their concerns are misplaced. They go on to make a distinction between perceptual and descriptive identification, a distinc- tion which we reject on the grounds that anything which comes into the discussion is both perceived and described. We are no% so much concerned about “ people’s conceptions of a physically given world. . . in connection with, their conception of a perceptually given world”, as with their conceptions (from our point of view) in connection with OUT description of the world. Again, we want a physical description in terms

S. Wilcox, D.A. Edwards / Psychology and physics: a reply 179

we (psychologists) understand (i.e., which has implications for our actions) which is commensurate with them (the people being studied).

In making their third point, that direct realism is not adequate, De Wit and de Swart get off on the wrong foot by misquoting us. We said that direct realism could be stated as the principle that “the objects of experience are properties of the world”, not “the objects of experience are the properties of the world”. Unlike their misquote, our statement contains the implication that there are other properties of the world besides those which are experienced. Therefore, when De Wit and de Swart trot out a version of Frege’s old war horse, the morning star and the evening star, they miss the point. Their view is that, as realists, we would be stymied by the fact that the same person could be described in two different ways - as “Mr. Smith” or “the person in front of P” (cf. Frege’s point that both the morning star and the evening star are really Venus). Their example really contains three points of view - I which contains “Mr. Smith”, 2 which contains “the person in front of P”, and 3 from which the equivalence of the first two is recognized. De Wit and de Swart seem to think that a direct realist would be forced to base his environmental description on 3 and thus be unable to account for 1 and 2. This is simply false. The three points of view would be described as “ tuning in” to different properties of the world, i.e., would involve different environmental descriptions. Of course, these environ- ments have certain relationships to each other which could also be described.

In any case, a direct realist is not forced to say perception is always veridical, only that veridicality cannot be handled in terms of correspon- dence to “external reality”. And the claim of direct realism is that perception is always incomplete, not the reverse.

De Wit and de Swart’s final points are that the notion of affordance is empty and that perceptual relativity requires the concept of “mental structure”. We will deal with the former shortly. De Wit and de Swart’s defense of the latter is that it is “hard to see” how it could be otherwise, a defense which is thoroughly question-begging. Gibson’s whole point was that an account of perceptual relativity is to be found by looking at an organism’s way of life, it’s past history, it’s needs, etc., rather than at the organism’s “cognitive structures” (cf. Wilcox and Katz 1981).

Hudson takes a different tack. He begins by criticizing us for failing to specify “which type of physics might be appropriate”, and, thus,

180 S. Wilcox, D.A. Edwards / Psychology and physics: a reply

risking the circularity inherent in explaining the perception of an object in terms of that object itself. Our response to this is that the object of perception is not the same as the explanation of perception. There is no problem of circularity, because the psychologist has a different point of view than the perceiver who is being studied. The perceiver sees chairs; the psychologist’s role is the development of a general theory which will allow him to specify when the perceiver sees a chair. The latter will typically involve some sort of reduction to elements which play a meaningful role in the psychological theory [2]. However, the Gibso- nian avoids the mistaken expectation that the psychologist’s elements play a role for the perceiuer. Likewise, the Gibsonian tries to choose elements that are of practical value for his own purposes, rather than those taken from some other science. Hudson accuses us of “saying that there exists some physics in which all this is possible, therefore we will postulate that it already exists and go on without worrying about it”. On the contrary, we see it as the psychologists’ role to develop this physics, or rather these forms of physics. We begin merely with the axion that such a thing is possible, a claim which is neither more nor less empirical than the alternative claim (grounded in the adherence to classical physics) that such a thing is not possible.

Hudson’s next point is that classical physics requires as few assump- tions as possible and should, therefore, be used as our base. He goes on to describe a body of research related to Gibson’s notion of ecological optics which involves, according to Hudson: (1) assumptions about “computations carried out by the perceive?, a notion which Gibson rejected, and (2) reduction to classical physics.

Let us say, at the outset, that our paper was not really about Gibson’s “ecological optics”, but rather his notion of an “affordance structure”. The two are quite different, and, in fact, in our discussion of the ambient array, we mentioned some of our reservations about ecological optics.

The development of ecological optics stemmed from Gibson’s early work with flight simulators. The problem was to build a dynamic two-dimensional display that would simulate real flight. He made a

[2] In practice, there will typically be some discrepancy between the description of environment and the description of an organism’s experience of it, simply to avoid making the environmental

description too cumbersome. But the Gibsonian does not expect to find a mechanism within the organism which either creates or eliminates this descrepancy, since it (the discrepancy) is merely a

product of the way the psychologist has chosen to describe things.

S. Wilcox, D.A. Edwards / Psychologv and physics: a reply 181

certain amount of progress using concepts such as texture gradients, occlusion, etc., and, of course, this work has now progressed to the point that very complex visual phenomena can be simulated and computer- based systems are capable of “perceiving” a wide variety of phenom- ena; work made possible, in part, by the further reduction of Gibson’s original concepts to the elements of classical physics. This is extremely impressive and important work. However, we disagree with the implica- tions Hudson draws from it. First of all, to claim that physics requires the fewest assumptions, and, we, therefore, must begin with it, assumes both that we can rank alternative environmental theories according to the number of required assumptions, and that we must choose the one with the fewest. We reject both assumptions. Again, what we need is a theory with the best chance of furthering the goals of our science. We are no more required than any other science to incorporate traditional physics into our discipline. Secondly, the fact that perceiving programs have been written which rely upon some of Gibson’s ideas and also entail internal computations only means that that is the way some systems have been designed. This has nothing to do with human perceivers. Finally, there is a difference between beginning with an ecological optics and reducing it to classical physics, and going in the reverse direction. The former is valuable for certain types of purposes, but how could one begin with classical physics and arrive at notions like slant and texture?

Huber repeats the standard view that “cognitive processes” entail sampling, comparing, etc. We argued that this whole view of mental phenomena stems from two beliefs - that explanation requires a certain type of atomism, and that experience begins with the apprehension of the elements of classical physics, rather than with the apprehension of a meaningful world. Since we reject this view, we don’t agree with Haber that reaction time is a useful way to tease apart supposed subprocesses.

We agree with most of the rest of Haber’s remarks, although we have a few reservations. There is no need to elaborate on the sense in which we reject an independence of organism and environment. We agree with Haber that we need a physical description, and that this does not require the use of classical physics. However, we still maintain that the historical inclination of psychologists to use “restricted choices” stems from their deference to physics. Indeed, it says a great deal about our field that “most of the few claims to lawful status yet available in psychology” have to do with the effects of changing simple parameters

182 S. Wilcox, D.A. Edwards / Psychology and physics: n reply

of isolated light and sound sources, etc. Finally, we agree that psychologists apply direct realism to them-

selves (indeed, otherwise it is hard to see how they could drive to work), but they certainly do not apply direct realism to their subjects (see Wilcox and Katz in press). For example, Helmholtz’s notion of the “stimulus” for perception was constrained by the retinal picture theory, as Haber points out. However, this was made possible by an epistemol- ogy inherited from Locke which saw experience as the dual process of obtaining primary qualities directly from the world and leaping beyond these by means of unconscious judgments, an epistemology normally referred to not as direct, but rather as, indirect realism, and, if his remarks about reaction time are any indication, Haber would seem to share this epistemology with Helmholtz.

Despite their differences, all three commentators agree in objecting to our failure to “specify the stimulus” beforehand. But, this “failure” is exactly what we believe is required. Any environmental description must be specific to the context of its use. It’s “physicality” stems not from a priori constraints, or from the elements which are used to describe it, or even , exactly, from the organism under study, but rather from its predictive power for the psychologist.

References

De Wit, H.F. and J.H. de Swart, 1983. Some perspective on the way that psychologists use

‘ecological physics’. Acta Psychologica 53, 171- 176.

Haber, R.N., 1983. Psychology cannot blame its theoretical mistakes on physics. Acta Psychologica

53, 155-162.

Hudson, P.T.W., 1983. A rose is a rose is a rose: minimalism in perception. Acta Psychologica 53,

163-169.

Wilcox, S. and D.A. Edwards, 1982. Some Gibsonian perspectives on the ways that psychologists

use physics. Acta Psychologica 52, 147-163

Wilcox, S. and S. Katz, 1981. What Gibson isn’t missing after all: a reply to Heil. Journal for the

Theory of Social Behavior 11, 313-317.

Wilcox, S. and S. Katz, in press. Can indirect realism be demonstrated in the psychological laboratory? Philosophy of the Social Sciences.